This study examines the interaction of dietary salt and psychological stressors on blood pressure and the physiological responses of plasma norepinephrine, epinephrine, renin, aldosterone, renal blood flow, and adrenergic receptor sensitivity. We shall study 4 groups of 20 men each: Whites with and without mild hypertension; and Blacks with and without mild hypertension. Our major hypotheses are: 1. that high salt intake increases the blood pressure response to psychological stressors, particularly in Blacks; 2. that hypertensive subjects' alpha and beta receptors are more sensitive to ambient levels of plasma catecholamines; 3. that hypertensive subjects respond to stressors with a fall in renal blood flow; 4. that hypertensive subjects respond to stressors not only with greater blood pressure elevation but also with greater increases in plasma catecholamines, renin, and aldosterone; 5. that suppressed hostility is associated with hypertension. Subjects will be studied at two extremes of dietary salt intake: 10 meq Na/day and 200 meq Na/day. All subjects will be studied twice, after stabilizing on each of the two diets. Diets will be administered and monitored at the Clinical Research Center of Massachusetts General Hospital. Subjects will be studied at rest, after postural challenge, and after psychological stressors.